The present invention relates to a method for modifying one surface of a textile fabric or a nonwoven fabric in which properties which are different from those of the above-mentioned textile fabric or nonwoven fabric itself are imparted to one surface of the fabric.
The above-mentioned method of the present invention is that in order to obtain a textile fabric or a nonwoven fabric suitable as a material of sportswear which is excellent in the perspiration treatment owing to an excellent function of moving a moisture from one surface to another in the fabric and has wash and wear properties, only one surface of the textile fabric or the nonwoven fabric is improved.
More specifically, the present invention relates to a method for modifying one surface of a textile fabric or a nonwoven fabric which is excellent in water permeability and diffusibility and which has a durability, wherein one surface maintains a hydrophobic nature inherent in the fibers and only the other surface is modified to have a hydrophilic nature (water absorption and sweat absorption) without accompanying an external change, a change in air permeability and the like.
In the human body, a moisture is always evaporated from the skin at normal state for regulation of the body temperature and due to a physiological perspiration function. In the vigorous sport, an amount of sweat is increased to prevent an abrupt increase of the body temperature.
Accordingly, a humidity within the clothing is also increased in taking part in a vigorous sport. It is said that when a temperature is 33.degree. C. and a humidity is 65% or more, sweat which reaches the body surface from the sweat gland cannot be gasified and perspiration in a liquid phase starts.
The increase in the amount of sweat inherently serves to decrease the increasing body temperature with evaporation heat. However, when sweat remains on the skin surface or retains on the clothing surface in contact with the skin, the regulation of the body temperature with evaporation heat does not function effectively, with the result that the temperature in the clothing and the amount of sweat are all the more increased.
On the contrary, when the body temperature starts to decrease after the sport, sweat which is present on the body surface or on the clothing surface in contact with the skin is evaporated to make one feel chill.
In order to prevent the uncomfortable feelings such as &lt;stuffy feeling&gt;, &lt;sticky feeling&gt; and &lt;chill feeling&gt; in or after the sport, the clothing is required which has such a comfort that sweat on the body surface can be absorbed quickly and released rapidly into the outside environment from the portion in contact with the skin.
When the conventional fiber materials are evaluated from this standpoint, a fiber material made of 100% of natural fibers of cotton, wool or the like absorbs sweat well because of the excellent water absorption. However, since this has an excellent water retention, sweat once absorbed is hardly evaporated, and a considerable amount of a moisture is left inside the fibers, so that drying takes much time. Meanwhile, a fiber material made of 100% of synthetic fibers has a low rate of water absorption when it is brought into contact with water, and has thus a poor water permeability. Accordingly, absorption or shifting of sweat is not conducted, inviting an uncomfortable feeling due to wetting with sweat.
A mixed fabric of natural fibers and synthetic fibers has also a defect that sweat absorbed is absorbed in natural fibers and a hydrous state is maintained, with the result that sweat (moisture) is hardly evaporated.
In order to solve these defects, a fabric in which one surface is hydrophobic and another is hydrophilic has been proposed.
FIGS. 1(A) through 1(C) are model views showing a water absorption and a water permeability of a hydrophobic textile fabric, a textile fabric in which both surfaces are hydrophilic, or a textile fabric in which one surface is hydrophobic and another is hydrophilic.
In the hydrophobic textile fabric of a fiber material made of 100% of synthetic fibers, a moisture permeation layer does not reach the outside as shown in FIG. 1(A). In the textile fabric of a fiber material made of 100% of natural fibers in which both surfaces are hydrophilic, a moisture permeation layer reaches the outside, and is uniformly distributed in the inside and the outside as shown in FIG. 1(B). In the textile fabric having the hydrophilic surface and the hydrophobic surface, the moisture permeation layer is enlarged from the hydrophobic surface to the hydrophilic surface as shown in FIG. 1(C).
With respect to the behavior of sweat truly required in the textile fabric for sportswear, working clothes entraining a large amount of sweat and the like, as mentioned above, what is important is not that sweat is absorbed into the textile fabric, but rather that sweat is moved from the hydrophobic surface in contact with the skin to the hydrophilic surface always in contact with open air without absorption into the textile fabric and is diffused and released into the surface layer. A fabric having a water absorption and a water permeability as shown in FIG. 1(C), namely, a fabric in which one surface is hydrophobic and another is hydrophilic can achieve such a behavior.
A variety of methods have been so far proposed for obtaining a textile fabric in which one surface is a hydrophobic surface and another is a hydrophilic surface. For example, it is known that in a post-treatment method in which a hydrophilic agent or a water-repellent agent is coated on one surface of a textile fabric, a textile fabric that does not give a stuffy feeling, a sticky feeling or the like can easily be produced. However, the textile fabric obtained by such a method has a poor washing resistance because the agent is simply coated thereon, and the textile fabric causes clogging by the agent coated, decreasing an air permeability.
A method has been also reported in which a textile fabric of synthetic fibers having a difference in function between front and back surfaces is obtained by imparting a hydrophilic nature to one surface of the textile fabric through plasma treatment using a low-temperature plasma method (for example, Japanese Patent Laid-Open Nos. 59-106,570 and 59-106,569). In this method, the textile fabric of synthetic fibers is fixed on an electrode surface in an inner electrode-type plasma device to treat one surface of the fabric. However, this method involves a problem that since the textile fabric has an air permeability, the overall fabric (both front and back surfaces) is plasma-treated in the plasma irradiation. Accordingly, no textile fabric having a satisfactory difference in function between front and back surfaces is obtained by such a method.